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by Polsdorfer R


A visual evoked potential test (VEP) is used to look for problems in the brain or nerves that affect vision. A machine records brain waves related to the nerves that make up the visual pathway.

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Reasons for Test

This test is often used to:

  • Diagnose and follow multiple sclerosis (MS)
  • Test vision in children and adults who are unable to read eye charts
  • Look for evidence of optic nerve damage, tumors or neuritis

There are many symptoms that might lead your doctor to order a VEP. You may be having double vision, blurred vision, or loss of part or all of your vision.

Possible Complications

There are no major complications associated with this procedure.

What to Expect

Prior to Test

You will be given instructions to prepare for the test, such as:

  • Wash your hair. Avoid hair chemicals such as hair sprays and gels.
  • Get a good night’s sleep.
  • Bring any corrective eyewear.

Description of Test

Wires will be attached to your scalp with tape. A patch will be placed over one eye. You will watch a screen with your other eye. The process is then repeated with the opposite eye covered.

The wires will be removed from your head.

After Test

You will be able to leave after the test is done.

How Long Will It Take?

About 45 minutes

Will It Hurt?



Your doctor will discuss the results with you and any further treatment that may be needed.

Call Your Doctor

Call your doctor if you have any concerns.

If you think you have an emergency, call for emergency medical services right away.


National Eye Institute (NEI)  https://nei.nih.gov 

National Multiple Sclerosis Society  http://www.nationalmssociety.org 


Canadian Association of Optometrists  http://www.opto.ca 

Canadian Ophthalmological Society  http://www.cos-sco.ca 


Evoked potentials (EP). National Multiple Sclerosis Society website. Available at: http://www.nationalmssociety.org/Symptoms-Diagnosis/Diagnosing-Tools/Evoked-Potentials. Accessed May 16, 2016.

Evoked potentials studies. Johns Hopkins Medicine website. Available at: http://www.hopkinsmedicine.org/healthlibrary/test%5Fprocedures/neurological/evoked%5Fpotentials%5Fstudies%5F92,P07658. Accessed May 16, 2016.

Visually evoked potentials. Webvision website. Available at: http://webvision.med.utah.edu/book/electrophysiology/visually-evoked-potentials. Updated July 14, 2015. Accessed May 16, 2016.

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